Flow-through analysis cell



Filed Nov. 15, 1968 United States Patent O 3,547,549 FLOW-THROUGH ANALYSIS CELL Heinz Engelhardt, Frankfurt am Main, Germany, assignor to Hartmann and Braun Aktiengesellschaft, Frankfurt am MainGermany, a corporation of Germany Filed Nov. 15, 1968, Ser. No. 776,122 Claims priority, application Germany, Nov. 24, 1967, 1,648,931 Int. Cl. G01n 1/10 U.S. Cl. 356-246 Claims ABSTRACT OF THE DISCLOSURE A flow-through analysis cell wherein analysis fluid flowing through a transparent tube is analyzed by radiation selectively absorbed by the fluid. Means are provided to enable a sheath-shaped stream of `indifferent fluid to flow in like direction with the analysis fluid but between the latter and the walls of the transparent tube to minimize deposits from the analysis fluid on the tube walls and promote clarity of the tube.

BACKGROUND OF THE INVENTION Field of the invention Analytical flow-through cell for radiation absorption by contents thereof, with parallel flow of indifferent fluid at cell inner walls.

Description of the prior art In photometric analysis 0f fluids in flow cells or cuvettes there is often the possibility of the adverse effect due to a coating forming on the inner wall of the cuvette tube which gives 'rise to an undue attenuation of the measured radiation passing transversely through the cuvette tube and its contents, and with consequent error in analyses utilizing absorption of radiation by fluids under study. This is especially true when the fluid being analyzedcontains dispersed or colloidal material.

SUMMARY OF THE INVENTION The invention minimizes formation of the above mentioned coatings or deposits by having an annular gap extending parallel to and situated substantially at the inner Wall of a cylindrical flow-through cuvette tube for adding a rinsing, scouring or flushing liquid to produce av thin rinsing or flushing layer of rinse liquid between the fluid being analyzed and the inner wall of the cuvette tube.

BRIEF DESCRIPTION OF THE DRAWING The drawing shows the invention in cross section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The flow-through cell comprises a cylindrical cuvette tube 1 substantially transparent to radiation and tted tight in a'bore 2 in the tail end of a block 3, the bore having a counter bore 2 through the remaining length and head face 3'. The portion 1 of the tube projects, exposed, from the block. The bore and counter bore form a hollow within the block which receives coaxially a round tubular 3,547,549 Patented Dec. 15, 1970 lCC Rinse or flushing liquid enters the annular space 2" through an open radial passageway 8 in the black and issues through the space 7 into the cuvette tube 1, as a thin cylindrical moving layer along the inner wall 1" of the cuvette tube. Analysis liquid enters the tubular piece 4 through an inlet tube 9 coaxial with the latter and with the cuvette tube, and passes out through the tail portion 6 inside the cylindrical moving layer of rinse liquid Without intermixing for a certain distance of travel.

The discharge portion 6 preferably extends at least as far into the cuvette tube as the exposed portion 1 so that the zone of non-mixing of fluids in the exposed portion is not shortened.

The rinse liquid itself should not produce any coating within the cuvette tube and should not disturb the radiation whose absorption properties are used in making measurements. In most instances water is suitable. The radiation passing through the cuvette tube should be in the zone of the latter where no mixing of the analysis liquid and rinse liquid occurs. This enables the rinse liquid to be continuously applied without any coating becoming built up on the cuvette inner wall 1 in the zone of absorption measuring that would influence the precision of measurement.

If the cuvette tube cell is not cylindrical then the space 7 is modified to correspond in cross-section for the rinse layer to provide a flow of the latter as a film at the inner wall as described for cylindrical cuvettes. Also the shape of rinsing layer flow inhibits turbulence or eddy currents which would otherwise result from the flow of the analysis liquid in round pipes or tubes such as 9 leading to the liquid to the cuvette having a cross-section other than circular. If the space 7 remained round, and the cuvette tube were not round, there would be turbulence and quick intermixing of the analysis and rinse liquids.

The space 7 at the issuing end may be on the order of a fraction of a millimeter in thickness. The bulk linear rate of flow of the rinse liquid is preferably less than that of the analysis liquid when the latter has a low flow-through rate because the liquid in actual contact with the cuvette wall will move, if at all, only by viscous flow and against surface tension. Under these circumstances, the analysis liquid tends to flow within a moving sheath of rinse or flush liquid and pass through the cuvette before the analysis liquid can appreciably diffuse through the sheath.

When there is much suspended matter in the analysis liquid it may be preferable to have the rinse liquid flow at an appreciable higher rate so as to impart a sort of scouring action on the Walls.

The analysis fluid may be of many types, such as liquid containing ferrie thiocyate as an indicator for amounts of iron, as Well as organic chemicals markedly absorbent of radiation of certain wave lengths.

The analysis fluid may even be gaseous, such as an air containing smoke particles or a gas characteristically absorptive of radiation. When the analysis passing through the cuvette tube is a gas the flow-through is preferably downwardly and the space 7 so narrow that the rinse liquid is of the nature of a falling film. The scouring may even be gaseous and the analysis fluid a liquid if both flow at suflicient speed. Generally, downward flow is preferable so as to reduce effects of any difference in density of the analysis and rinse fluids, though at high rates of flow the device may be horizontal.

I claim:

1. A flow-through cell for analysis fluid comprising a flow-through, generally exposed, cuvette tube transparent to radiation, a mount for the tub receiving same fluidtight, a tubular member in the mount and having a discharge end-portion in axial alinement with cuvette tube for passing analysis fluid into and longitudinally through the tube, the mount being provided with a hollow having an inlet opening for receiving a second fluid, the hollow receiving and axially surrounding the tubular member to provide at said end portion a perimetric discharge jet-like space open toward the interior of the tube and generally parallel with the inner walls of the cuvette tube for providing a thin film of the second uid to flow along with the analysis uid and between and parallel with the tube walls and analysis uid as the latter flows the cell to separate the analysis uid from substantial contact with the walls for at least a portion of the length of the eX- posed tube.

2. A cell as claimed in claim 1, wherein said discharge end portion partially projects into said tube.

5 of the discharge end portion and the adjacent portion of the cuvette tube are circular.

References Cited Gucker et al: A Photoelectric Counter for Colloidal Particles, The American Chemical Society Journal, vol. 69, pp. 2422-2431, October 1947.

RONALD L. WIBERT, Primary Examiner 3. A cell as claimed in claim 1, wherein said discharge 15 O. B. CHEW II, Assistant Examiner 

